1. Field of the Invention
This invention relates generally to an infrared photon detector and, more particularly, to an instrument for detecting and counting infrared photons having an energy of about 1 electron volt.
2. Discussion of the Related Art
Photon-counting detectors operating in the visible, ultraviolet and x-ray region of the radiation spectrum play an extremely useful role in astronomy and physics. With deep-space communications becoming a necessity in the near future as space-travel develops, photon-counting detectors will be essential. Present photon-counting techniques utilize the photoelectric effect to relate the ejected photoelectron current to the incident photon flux. However the energy of the detected photons must exceed the detector-metal-work-function, which, for the metal with the smallest work function, Rubidium, is 2.16 electron volts. Therefore photons with wavelengths longer than 0.425 microns will not be detected by a photon counter. Unfortunately, most popular solid-state lasers that are used in communications at present, operate at about 1 micron wavelength corresponding to a photon-energy of about 1.2 electron volts. Infrared detectors, based on semiconductor materials, do exist. In these, the work-function energy is replaced by the band-gap energy that exists between the semiconductor""s valence and conduction bands. If the absorbed photon""s energy exceeds the band-gap energy, a hole-election pair is created that is detected by the electrical apparatus connected to the semiconductor. Unfortunately, there are other means of generating hole-electron pairs in semiconductor detectors in addition to photon absorption, that make single-event infrared photon counting impossible.
What is needed, therefore, is an instrument for detecting and counting individual visible and infrared photons having energies less than 2 electron volts that can operate at room temperature.
In accordance with the teachings of the present invention, a detector for detecting infrared photons with an energy approximating 1 ev is disclosed. The detector comprises a glass tube having an aperture for receiving the infrared photons and enclosing an anode, a gate electrode, a cathode, and a dynode multifier chain. The cathode comprises a plurality of carbon nanotubes with a conductive film that electrically connects the nanotubes. The anode, gate electrode and cathode are biased such that when infrared photons are absorbed by the nanotubes, photoelectrons are created. The flow of photoelectrons within the glass tube is controlled by the gate electrode and multiplied by the multiplier chain. A counter is included for counting the multiplied photoelectrons.
Additional objects, advantages and features of the present invention will become apparent from the following description and appended claims, taken in conjunction with the accompanying drawings.